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KMID : 0578319940040030321
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Molecules and Cells
1994 Volume.4 No. 3 p.321 ~ p.326
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Alteration of Serum insulin-like Growth Factor Binding Protein-3 (IGFBP-3) in Pregnancy
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Lee, Dae-Yeol
Kim, Ran-Ju/Hwang, Pyung-han/Rheu, Cheol-hee/Kim, Jung-Soo
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Abstract
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The insulin-like growth factors, IGF-I and IGF-II, are bound by several binding proteins (IGFBPs) that appear to regulate IGF transport, receptor binding and action. To characterize the serum IGFBPs pattern in pregnancy, we used western ligand blot (WLB) and western immunoblot (WIB). There was a marked decrease in serum level of IGFBP-3 analyzed by WLB, after 6 weeks of gestation, continuing to term and returning to a nonpregnant level by 10 days postpartum. Serum IGFBP-3 WIB profiles were remarkable for 30 kDa fragments of IGFPB-3 seen in pregnancy serum but not in non-pregnancy serum. To evaluate whether an IGFBP-3 protease accounts for the absence of intact IGFBP-3 in pregnancy serum, we did a protease assay. Incubation of term pregnancy serum with non-pregnancy serum showed a marked reduction of IGFBP-3. Ukewise, incubation of rhIGFBP-3 with term pregnancy serum revealed a significant decrease in IGFBP-3 and production of proteolytic fragments. IGFBP-3 proteolysic activity in pregnancy serum was markedly inhibited by PMSF, EDTA, aprotinin, but not by pepstatin. This pattern of inhibition is consistent with a metal-dependent serine protease. We conclude that the decrease in intact IGFBP-3 is due to proteolysis by a protease and the proteolysis of IGFBP-3 may alter the bioavadability of the IGFs in the maternal tissue and contribute to the altered metabolic demands of pregnancy.
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